Latices of natural rubber, synthetic rubber, acrylates, and ethylene vinyl-acetate type polymers have been used to make foams for backing carpet or curtains, to improve the tuft lock of carpet and to adhere secondary backing to carpet. The present invention seeks to provide new compositions suitable for such applications which include latex modified with asphalts.
British Pat. No. 332,525 accepted July 31, 1930, in the name of the Dunlop Rubber Company, discloses a process for manufacturing foam rubber using heat sensitive gelling systems such as ammonium persulfate or delay action gelling agents such as sodium silicofluoride.
British Pat. No. 332,526 accepted July 31, 19830, in the name of the Dunlop Rubber Company, discloses a process for making foam rubber merely by heating a foamed latex.
Since July 31, 1930 foam rubber has found a number of applications including upholstery and carpet backing.
It is known to extend rubber and latex with mineral oil. Generally the oil is a highly refined oil and is used in amounts from about 5 to 25 parts by weight per 100 parts by weight of rubber in the latex. Typical of the types of extending oils which may be used in association with latex foam are those listed in U.S. Pat. No. 3,107,224 issued Oct. 15, 1963 and assigned to the Goodyear Tire and Rubber Company.
It is known to add lactices of polymers such as styrene-butadiene or butadiene-acrylonitrile to emulsions of tar, asphalt or bitumen. Typically, the latex is added in amounts to provide a rubber content of less than 10 percent, preferably less than 5 percent, on a dry weight basis. The modification of tars, asphalts and bitumen provides improved properties to the resulting tar, asphalt or bitumen. Representative of this art is U.S. Pat. No. 3,027,342 issued Mar. 27, 1962, assigned to the Koppers Company Inc.
British Pat. No. 2,006,220 issued Mar. 3, 1982, assigned to the British Petroleum Company, discloses a hardened bitumen modified with a mixture of a thermoplatic and a non-thermoplastic rubber. The bitumen composition is then heated to produce cellular foam.
In the field of carpet backing, there is a requirement for a lower price composition which may be applied directly to the back of a carpet to improve tuft lock and optionally to adhere a scrim backing. Additionally, it would be desirable to develop a material which could be applied to carpet backing as an aqueous based froth which could be set and dried to a rubber type foam.
There is nothing in the prior art which would suggest that a latex of an elastomeric polymer could be extended with an emulsion of asphalt, tar or bitumen.